What is the difference between JAVA and BEDROCK Edition Minecraft?

I have to decide if I buy Bedrock or Java Minecraft because I do not know much about Minecraft

The Java Edition is, so to speak, the "original". That means you have access to all the mods and community servers that have been developed over the years. Accordingly, this would also be my recommendation if you want to play the game normally on the PC.

The Bedrock Edition is basically a generic term for multiple platforms. Including the mobile versions, Xbox or as a separate version of Windows 10. Bedrock Edition players have crossplay between each edition of Bedrock.